This application claims the priority of International Application No. PCT/DE2008/000968, filed Jun. 6, 2008, and German Patent Document No. 10 2007 029 491.5, filed Jun. 26, 2007, the disclosures of which are expressly incorporated by reference herein.
The invention relates to a method and a device for surface peening, in particular for ultrasonic shot peening, of a component in the region of a passage opening.
Such a method and such a device are already known, for example, from German Patent Document No. DE 10 2004 059 592 A1. In it, a device is used which comprises a vibration device in the form of an ultrasonic sonotrode for impinging or accelerating the blasting material, as well as respective counter-elements. To peen the passage opening, the vibration device is disposed on one side and the respective counter-element is disposed on the opposite side relative to a component region having the passage opening. The peening of the component is then done in two steps. During the first step, the marginal region facing the vibration device is peened between the surface of the corresponding side of the component region and an inner surface of the passage opening. A counter-element is used for this which is inserted in the passage opening like a hatch pin. The counter-element and the passage opening therefore have substantially identical cross-sections.
In a second step, another type of counter-element is used which, on the side of the component opposite the vibration device, lies plane on the corresponding surface of the equivalent component region. Overall, as a result of the two steps of the surface peening, homogeneous strengthening of the surfaces in the region of the passage opening is to be created, in order to create a connection of the component—a rotor blade of a gas turbine in that invention—which is extremely resistant to failure due to crack formation.
The aim of the present invention is to create a method and a device of the type described above by means of which particularly reliable and uniform strengthening of the component region having the passage opening can be achieved.
To allow extremely reliable and uniform strengthening of the component in the region of the passage opening, in the method in accordance with the invention the counter-element is disposed at a distance to the corresponding side of the component region. In other words, in accordance with the invention the counter-element, in contrast to the prior art in accordance with DE 10 2004 059 592 A1, is not to be positioned directly on the corresponding surface region of the component and instead a corresponding distance must be provided for.
It is therefore achieved in an extremely simple and reliable way that, for example, a marginal region between a surface of the corresponding side of the component region facing the counter-element and an inner surface of the passage openings are uniformly surface peened. In conjunction with that, satisfactory rounding of a marginal region that was originally substantially angular in cross-section can be achieved so that it has a desired rounding or a corresponding radius after the surface peening has been done.
As a result of the distanced arrangement relative to the equivalent surface of the corresponding side of the component region, it is, moreover, achieved that the surface close to the passage opening is also particularly reliably strengthened. A further advantage is that both of the opposing marginal regions between the respective surfaces and the inner surface of the passage opening can be simultaneously surface peened, so that the entire component can be worked in one processing step in the region of the passage opening.
In particular, the present invention creates a method that can provide targeted treatment of passage openings or bore holes in components made of basic aluminum alloys, which tend to develop cracks in the event of, for example, corresponding vibrational stress and/or static force or the application of pressure. It is thus very important in the case of such components to be able to induce a homogeneous residual compressive stress profile in the region of the passage opening. That is achieved in a particularly advantageous way using the present method.
The counter-element is preferably also constructed as a sonotrode, which in addition to the aforementioned advantages, leads to greater homogeneity of the peening results and to a reduction in peening time.
In a further arrangement of the invention, it has also been shown to be advantageous when a non-planar inner side of the counter-element facing the passage opening is used by means of which a marginal region between a surface of the corresponding side of the component region and an inner surface of the passage opening is surface peened. In other words, by using a non-planar inner side of the counter-element, it is achieved that the marginal side between the respective surface of the component and the inner surface of the passage opening can be ideally strengthened or rounded. It is naturally achieved in addition that the inner surface, particularly in the upper region—i.e., near the counter-element—is also peened particularly well and uniformly.
In a further arrangement of the invention, it has also been shown to be advantageous when a deflection tool is disposed in the passage opening. As a result of such a deflection tool, whose cross-section is dimensioned smaller than the corresponding passage opening, targeted deflection of the blasting material that is accelerated by the vibration device in the direction of the inner surface of the passage opening is achieved so that the latter is particularly reliably and homogeneously strengthened.
In that context, it has also been shown to be positive if the deflection tool is disposed in the passage opening from the side of the counter-element. As a result, the deflection tool is preferably positioned on the side opposite the vibration device so that the blasting material accelerated by the vibration device is deflected in a particularly advantageous manner by means of the deflection tool, particularly in the direction of the inner surface of the passage opening.
It has also been shown to be advantageous when the deflection tool is disposed jointly with the counter-element relative to the surface region of the component having the passage opening. This results in an arrangement of the counter-element and the deflection tool which is particularly simple with regard to process technology, whereby it can also be ensured in a simple manner that the counter-element and the deflection tool are always constantly positioned relative to each other. This therefore allows particularly good reproducibility of the surface peening to be ensured. In that context, it has been shown to be particularly advantageous in a further arrangement of the invention when the deflection tool and the counter-element are constructed as one piece.
The deflection tool whose cross-section is dimensioned smaller than the passage opening is also preferably disposed in a central region of the passage opening so that it has a distance to the corresponding inner surface of the passage opening that is preferably uniform toward all sides. Particularly homogeneous strengthening of the inner surface of the passage opening is achieved as a result.
It is also advantageous when the deflection tool is disposed over a partial length of the passage opening within the latter. Because experience shows that the inner surface of the passage opening is sufficiently strengthened near the vibration device, it is particularly necessary that the deflection tool is positioned in the partial length of the passage opening which is disposed farther from the vibration device. Consequently, overall, an extremely homogeneous or uniform strengthening of the inner surface of the passage opening is ensured by a deflection tool positioned over only a partial length of the passage opening.
It is also advantageous when a surface of the vibration device impinging the blasting material is disposed at a distance to the corresponding side of the surface region of the component. It can thereby be ensured that the surface of the corresponding side of the component region facing the vibration device or a marginal region between that surface and the inner surface of the passage opening is particularly reliably strengthened or rounded. Thus, if, overall, both the counter-element and the vibrating surface of the vibration device are disposed at a respective distance to the corresponding surface of the component, particularly reliable strengthening of the two marginal regions between the respective surfaces and the inner surface of the passage opening can be achieved.
To achieve a particularly advantageous strengthening of the component in the region of the passage opening, it has also proven to be advantageous when the surface region of the component having the passage opening is disposed substantially horizontally and the vibration device is disposed below the surface region.
Finally, a method has proven to be advantageous in which the component region is positioned within a peening chamber in which the vibration device and the counter-element are also disposed in addition to it. As a result of such a peening chamber, the quantity of blasting material can be kept uniform in a simple manner, so that an extremely reproducible peening result can be obtained.
The advantages described above in connection with the method in accordance with the invention also apply to the device. It is also distinguished in particular in that, in addition to the vibration device, at least one counter-element is used which is positionable at an equivalent distance to the corresponding side of the component region. It is clear that such a device can be designed both as a static unit that remains stationary and as mobile equipment. Accordingly, with the static arrangement of the device, the component is positioned on the device—relative to the vibration device and the counter-element—while a mobile device is disposed relative to a stationary component.
The deflection tool that is described above has, in a further arrangement of the invention, on its free end a deflection point that also ensures that blasting material that is accelerated by the vibration device moves in the direction of the inner surface of the passage opening in a particularly advantageous manner.
Finally, it has also proven to be advantageous in the device in accordance with the invention when a holding device is provided by means of which the surface region of the component having the passage opening can be disposed relative to the vibration device or the counter-element.
Additional advantages, features, and details of the invention are contained in the description below of a preferred example of an embodiment and in reference to the drawings.